Commuters roller-bladed, drove and biked to work, or simply stayed home Thursday, as the biggest strike in 12 years crippled France's public transport system and handed President Nicolas Sarkozy the biggest political test of his young presidency.

The unrest, which came on the same day Sarkozy announced his divorce, appeared set to continue for a second day and showed that the president's ambitious plans to reform France won't be smooth sailing.

The government was unbowed in its determination to scrap special retirement privileges for some state workers — but unions, too, stood firm, hoping to repeat past successes in blocking efforts to erode their generous benefits.

As the president left town for Portugal on Thursday for an EU summit, his compatriots were left in a nation immobilized:

More than 90 percent of high-speed TGV trains were not running. Only one Paris subway line — which is automatic, with no drivers — was running as usual. Train service to and from Britain and Belgium and beyond was limited, though only moderately, by the strike.

Thousands of marchers, many blowing bullhorns or setting off firecrackers, took to the streets Thursday in Paris — one of dozens of similar protests across the country in support of the strike.

As the workday wound down Thursday, the key question was how much momentum the strikers had to go on.

Paris subway workers voted to extend the strike — originally scheduled to last 24 hours — to Friday, and electricity sector workers were joining in. The SNCF national rail authority said train traffic nationwide would gradually return to normal Friday but predicted continued disturbances throughout the morning.

The dispute centers on Sarkozy's plans to scrap a special pension plan initially meant to give advantages to those in physically tough jobs, such as miners and train drivers. They are able to retire earlier — and on more generous terms — than the vast majority of France's working population.

The government insists that reforms are needed to keep the pension plan afloat for hundreds of thousands of workers who benefit from it.

Over a single day, strikes aren't too intolerable: Many workers simply take off the day and count it against their relatively high number of vacation days.

"If it lasts a day, it's no big deal," said Francine Mirano, a secretary from a Paris suburb, as she arrived on one of the few trains running. "But if it goes on for a long time, that's annoying."

In 1995, strikes against a bolder plan to reform retirement rights dragged on for three weeks, punishing the prime minister and sapping then-President Jacques Chirac's appetite for reform.

In France, where the right to strike is widely seen as sacrosanct, even some commuters expressed support for the strikers.

"I agree with this strike," said engineer Annie Proy. "Afterward, the government will attack the rights of other workers."

With trains stuck in depots, many people took to bicycles, scooters, even rollerblades to get to jobs in the capital. In the suburbs, many people appeared to have taken the day off or were working from home.